1. Field of the Invention
This invention relates to recording holograms and, more particularly, to a system and method for synchronizing a spatial light modulator with the pulsed laser to record a hologram at the repetition rate of the pulsed laser for application including holographic displays and data storage.
2. Description of the Related Art
Holography is a technique that allows the light scattered from an object to be recorded and later reconstructed so that it appears as if the Object is in the same position relative to the recording medium as it was when recorded. Alternately, holograms can be computer generated by calculating the modulation pattern that would have been formed if beams with certain characteristics (wave front, intensity) would have crossed each other. The calculated pattern is next transferred to a medium to make the actual hologram. The image changes as the position and orientation of the viewing system change in exactly the same way as if the object were still present, thus making the recorded image (hologram) appears three-dimensional. The technique of holography can also be used to optically store, retrieve, and process information.
As shown in FIG. 1, when two coherent optical beams e.g. a reference beam 10 and an object beam 12 of finite beam width cross each other at a point in space, they interfere. The phase difference between the beams at each spatial location defines the intensity pattern. The recording of this intensity variation into a holographic recording material 14 as a phase and/or intensity modulation results in the formation of a hologram 16. The object beam may be scattered from the object or modulated with a spatial light modulator (SLM) based on computer-generated images to produce an image or to store information. The optical beams may be continuous wave (CW) or pulsed lasers. Typical holographic recording materials include silver halide emulsion films, photothermoplastics, photopolymers, photochromics material and photorefractive (PR) material, including polymers. To store large amounts of data or to write a 3D image by integral holography, a large number of holograms have to be recorded side-by-side. Each hologram is a holographic pixel (or hogel) of a larger frame.